This invention relates to fusing toner images and more particularly to a heat and pressure roller fuser for fixing toner images to copy substrates.
The invention can be utilized in the art of xerography or in the printing arts. In the practice of conventional xerography, it is the general procedure to form electrostatic latent images on a xerographic surface by first uniformly charging a photoreceptor. The photoreceptor comprises a charge retentive surface. The charge is selectively dissipated in accordance with a pattern of activating radiation corresponding to original images. The selective dissipation of the charge leaves a latent charge pattern on the imaging surface corresponding to the areas not exposed by radiation.
After the electrostatic latent image is recorded on the photoconductive surface, it is developed by bringing a developer material including toner particles into contact therewith to thereby form toner images on the photoconductive surface. The images are generally transferred to a support surface such as plain paper to which they may be permanently affixed by heating or by the application of pressure or a combination of both.
One approach to thermal fusing of toner material images onto the supporting substrate has been to pass the substrate with the unfused toner images thereon between a pair of opposed roller members at least one of which is internally heated. During operation of a fusing system of this type, the support member to which the toner images are electrostatically adhered is moved through the nip formed between the rolls with the toner image contacting the heated fuser roller to thereby effect heating of the toner images within the nip. As will be appreciated, in a machine where duplex images are created both rolls may be heated. In either case, one of the rolls is usually referred to as the fuser roller while the other is commonly referred to as a pressure or back-up roll.
As Xerographic or electrostatographic machines become smaller and smaller, there is a need to make fusing apparatus with smaller and smaller fuser rollers, as well as a need to make such a fusing apparatus economical and efficient.